Stress relaxation processes are one of the reference tests for the determination of bond exchange kinetics of covalent adaptable networks (CANs), which are needed for the definition of adequate reprocessing scenarios. We recently developed a kinetic-structural model, based on an analogy with a decrosslinking process, capable of successfully describing a wide range of stress relaxation scenarios depending on (i) the network architecture, (ii) the presence of permanent bonds and (iii) the coexistence of relaxation processes with different bond exchange kinetics [1]. In this work, we take a step further and show the possibility of making quantitative predictions of stress relaxation kinetics and relaxation times. For that purpose, we choose dissociative CANs based on furan-maleimide Diels-Alder networks for which detailed reaction kinetic data are available [2]. The network formation and crosslink density are calculated using the reaction kinetics and monomer descriptions and validated with experimental rheological data. Then, the stress relaxation curves are calculated at different temperatures and compared with experimental data from rheological analysis. It is shown that the model is capable of producing accurate predictions of the relaxation kinetics of different polymer networks starting only from (i) the composition and architecture of the network, (ii) the kinetics of the retro Diels-Alder reaction and (iii) a single parameter, common to all the networks studied, reflecting the effect of the strain-induced stress on the bond exchange kinetics. This model can be extended to the analysis of dissociative CANs with more complex network architectures.

Formo-phenolic resins are historically significant synthetic materials known for high mechanical strength and thermal stability.¹ Although, they derived from non-renewable petroleum and non-recyclable resources. To address these limitations, the introduction of dynamic covalent bonds within a chemical network² offer reprocessability and repairability while keeping excellent thermo-mechanical properties.³ Herein, we prepared reprocessable phenolic resins containing dynamic phenol-carbamate crosslinks starting from commercial novolac resin and partially biobased polyisocyanates, using dibutyltin dilaurate (DBTDL, 1wt.%) as a catalyst. The resulting phenolic-based CANs achieve good mechanical properties (up to 90 MPa) and high glass transition temperature (Tg up to 175°C) with the added benefit of rapid stress relaxation (relaxation times of a few seconds at T ≥ 200°C). Characterization by FTIR, stress relaxation experiments, and mechanical tests demonstrated that these CANs can be reprocessed up to three times maintaining good properties. Additionally, commercial novolac was replaced with a biobased cashew nut shell liquid (CNSL) novolac⁴ leading to a reprocessable/recyclable material with a high and biobased content (up to 87 wt%). The phenol-carbamate CANs hold promise for applications in recyclable, easily repairable resin matrices for molding compounds and glass fiber composites, enhancing both processability and environmental sustainability.

Epoxy-based resins are widely exploited for high-performance and demanding applications due to the development of a dense, permanent crosslinked structure after cure. However, these resins cannot be recycled, reprocessed, dissolved or self-healed once synthesized and thus, the sustainable management of thermoset waste still remains a challenge. Lately, the introduction of dynamic covalent bonds emerged as a sustainable approach for combining high-performance materials with (re)processability and repairability[1-4]. In this perspective, Leibler and co-workers pioneered the concept of vitrimers[1], insoluble thermoset-like materials at service temperature capable also of flowing under stimuli (heat, pressure, light) via associative bond exchange reactions[1-3]. Epoxy-based vitrimers are well documented in the literature, but usually they are cured with long-chain dicarboxylic acids (e.g., fatty acids[1], sebacic[5] and glycyrrhizic acid[6]) which yield relatively low Tg and elastic mechanical behavior at room temperature. These elastic vitrimers cannot meet the requirements for high-performance composites used in construction and automotive industries and therefore, new epoxy-acid systems should be explored.
To realize this concept, a series of epoxy-based vitrimers was developed from diglycidyl ether of bisphenol A (DGEBA) and bio-based succinic acid. Succinic, being a short-chain acid, allowed the formation of a densely crosslinked network (Tg ~ 94-133 °C) combined with a small statistical distance between hydroxyl-ester moieties therefore fast reprocessing/relaxation (e.g., 700 s at 160 °C). By tailoring the molar ratios of the reactive end-groups (1:0.25, 1:0.5, 1:0.75 and 1:1 with respect to the oxirane ring), catalyst type [Zn(acac)2 or Sn(oct)2] and concentration, crosslink densities, mechanical and viscoelastic properties were readily manipulated.

Vitrimers are a new emerging class of polymeric materials at the border between thermoplastic and thermosetting materials. While they have high mechanical and chemical robustness at room temperature, they are typically reprocessable at high temperature. These properties make vitrimers highly valuable materials, especially if they are synthesized from renewable carbon sources[1].

The Netherlands has a strong agricultural sector, where the most abundant biomass is composed mainly of polysaccharides and their derivatives (such as cellulose or amylose). However, polysaccharides exhibit poor mechanical properties, hence limiting their potential applications. In this context, the combination of biomass and chemically recycled end-of-life plastics could provide a sustainable pathway[2],[3] for the production of highly valuable vitrimers (while valorizing wastes), with excellent mechanical performance and recyclability.

Therefore, in the present work, hybrid vitrimers were prepared from two building blocks, namely, biomass and end-of-life plastics. The biobased building blocks were synthesized using oligosaccharides (cellodextrin obtained from cellulose depolymerization or amylose because of their abundance) partially modified with glycidyl methacrylate (GMA), leaving both methacrylate moieties and pendant reactive alcohols throughout the backbone. We aimed to bring high mechanical strength by using a second building block, namely, terephthalic acid (obtained from depolymerized PET) and GMA, leading to a dimethacrylate aromatic building block. The final hybrid network prepared from these building blocks exhibited high mechanical strength and could be reshaped via dynamic transesterification reactions[4] while valorizing biomass and end-of-life plastics.

Vitrimers represent a promising class of sustainable alternatives to conventional thermosetting polymers due to their reprocessability and recyclability. In this study, a bio-based vitrimer nanocomposite was explored, consisting of a glycerol (GTE) resin and a vanillin-derived imine hardener (VA). The recyclability is facilitated by a catalyst-free imine metathesis mechanism.
Dynamic exchange reactions, which are the basis of vitrimer recyclability, remain poorly understood, with molecular mobility being a critical factor. This study investigates molecular mobility using broadband dielectric spectroscopy (BDS) to provide insights into the molecular mechanisms governing these exchange reactions.
Despite the inherent advantages of vitrimers, their flame retardancy is typically limited, hindering their applicability in high-performance sectors. To address this challenge and enhance their thermomechanical properties, nanoparticles and a flame retardant were incorporated into the matrix. Specifically, boehmite (AlOOH), sidistar (SiO₂), and EDA-DOPO were added.
A combination of thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TG-FTIR), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and small- and wide-angle X-ray scattering (SAXS/WAXS) was employed to investigate nanoparticle dispersion and their effects on the macroscopic properties of the composites. Flammability and fire behavior were further characterized using cone calorimetry, UL-94, and limiting oxygen index (LOI).
These findings provide novel insights into the dynamics of exchange reactions while demonstrating a promissing strategy for enhancing both flame retardancy and thermomechanical performance through nanoparticle integration. These results expand the potential applications of vitrimers in high-performance, fire-safe environments, advancing their role in sustainable material design.

The precise construction of complex and hierarchical polymeric nanostructures is pivotal for enabling advanced functionalities, such as those seen in biomimetic systems and targeted drug delivery. Traditional polymer self-assembly methods, constrained by single driving forces, often yield limited morphological diversity. In this study, we integrate crystallization-driven self-assembly (CDSA) with supramolecular interactions to achieve multiscale hierarchical nanostructures under mild, stimulus-independent conditions. This novel approach provides unprecedented control over morphology and structural complexity, enabling the formation of polymeric architectures with tailored functionalities. Such control is particularly significant for applications in drug delivery systems, molecular motors, and therapies for neurodegenerative diseases, where precision and adaptability are crucial. By bridging molecular-level interactions and macroscopic design, this work establishes a robust platform for engineering next-generation polymeric nanostructures with broad application potential.

Vitrimers, which are polymeric networks containing dynamic covalent bonds capable of rearranging their topology in response to stimuli [1, 2], have garnered significant interest in the development of sustainable materials with enhanced mechanical and processing properties. Despite this, the viscoelastic behaviour of vitrimers, particularly the temperature-dependencies of the storage and loss moduli, remains to be understood. Existing models for supramolecular chemistries have failed to fully explain experimental data, highlighting the need for novel approaches to elucidate their viscoelastic properties [3].

This project seeks to investigate the mechanical properties and dynamics of polystyrene samples with varying dioxaborolane cross-linker contents. By employing the Time-Temperature-Superposition (TTS) principle, we aim to determine the apparent activation energy for flow. Furthermore, the impact of molecular weight and backbone chemistry on material properties is further explored.

Based on these experimental results, we adapt the Time-Marching Algorithm (TMA) tube model [4, 5] to integrate dynamic covalent bonds into the polymer network. Our objective is to establish a theoretical framework for understanding the relationship between cross-linking density and activation energy for flow in vitrimers. This research endeavours to fill knowledge gaps regarding the properties and dynamics of vitrimers, with the ultimate goal of facilitating their future industrial and commercial applications.